This invention relates to a power transmission system for an inboard/outboard motor and more particularly to an improved transmission and clutch system for the outboard portion of an inboard/outboard drive.
A well known type of inboard/outboard drive includes a outboard drive that is mounted on the rear of the transom of the watercraft for steering movement about a vertically extending axis and tilt and trim movement about a horizontally extending axis. A universal joint couples an output shaft of a hull mounted internal combustion engine to an input shaft of this outboard drive unit. Conventionally the outboard drive unit employs a bevel gear forward, neutral, reverse transmission mounted on the input shaft and which drives the drive shaft in selected forward or reverse directions. Some form of clutch mechanism is incorporated for coupling the driving bevel gears to the input shaft so as to drive the drive shaft in the selected direction.
In connection with such transmissions, there are certain advantages in employing hydraulic actuators for the clutch mechanism. Such hydraulic actuators permit ease of application and permit high power outputs to be transmitted through the transmission- However, when a hydraulicly operated clutch or clutches are employed, it is necessary to provide a pump for pumping the hydraulic fluid and a selector valve for selectively pressurizing the clutches.
If the pump and valve are mounted in the outboard drive unit, as is desireable, their actual positioning can present some problems. It is desirable, if not essential, to drive the pump off of the input shaft so that it will be continuously operated. However, if the pump and valve are positioned forwardly of the bevel gear transmission, then the drive shaft is moved a considerable distance from the stern and this adversely effects the steering of the watercraft and also makes the forward portion of the outboard unit extremely heavy and gives rise to problems for servicing. That is, if it is desired to remove the entire outboard drive portion from the hull, the heavy forward weight of the universal joint and hydraulic system comprised of the pump and valve make manipulation difficult due to the nose heavy construction. On the other hand, if the pump and valve are positioned in axially alignment with the forward neutral reverse transmission, then the pump and valve must be positioned above the transmission and this give rise to considerable height of the unit which has undesirable effects.
It is, therefore, a principal object to the invention to provide a hydraulic actuating system for an outboard transmission that will provide good balance, compact construction and ease of handling.
It is a further object to this invention to provide an improved arrangement for driving and controlling a hydraulic pump for an outboard drive that will achieve these results.
In connection with outboard drives of the type described, it is generally the practice to provide some mechanism for lubricating not only the gears of the transmission but also the gears or transmission which drives the propulsion unit from the drive shaft. Various types of pumping arrangements have been employed for this purpose. However, when such separate pumps are employed then the system becomes quite complicated and expensive.
It is, therefore, a still further object to this invention to provide an improved outboard drive for a marine propulsion unit wherein a single pump not only circulates lubricants through the system but also provides the motive power for actuating the transmission.
In connection with the construction of marine outboard drives and particularly those having bevel gear transmissions and clutches, it is desirable to provide a housing assembly for the outboard drive that will have a minimum number of parts and yet permit ease of assembly of the components. In addition, the arrangement must by such so as to permit adequate clutch discs to be employed so as to be capable of transmitting high driving forces. Furthermore, the use of bevel gear transmissions gives rise to axial thrust on the gears during their driving operation. These axial thrusts act in either the same or opposite directions to the operation of the associated clutches. Therefore, it is desirable to insure that the axial thrust on the bevel gears of the transmission will not adversely effect the operation of the clutches.
It is, therefore, a still further object to this invention to provide an improved outboard drive that will permit a compact construct, a simple housing assembly and ease of assembly.
It is a further object to this invention to provide an improved bevel gear type of transmission for a marine outboard drive and yet the use of clutches having large effective areas to transmit large degrees of power.